Cooling tower water distribution system

ABSTRACT

A cooling tower is provided having a heat exchange section. A water collection basin located above the heat exchange section. The water collection basin has a plurality of openings that allow water to be distributed downwardly onto the heat exchange section. The water collection basin openings each have a diameter of from 0.2 inch to 0.6 inch.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of prior U.S. patent application Ser.No. 15/373,647, filed Dec. 9, 2016 which is hereby incorporated hereinby reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to an improved spray waterdistribution system that is used within evaporative heat exchangeapparatus such as cooling towers, closed circuit fluid coolers, fluidheaters, condensers, evaporators, thermal storage systems, air coolersor air heaters.

Some evaporative heat exchange apparatus use gravity fed, unpressurizedspray water distribution systems to wet the surfaces of the direct orindirect heat exchangers. The water is sprayed from above the direct orindirect heat exchanger and generally flows downward to wet varioussurfaces of heat exchanger. Air is drawn or forced over the wettedsurfaces of the heat exchanger causing both latent and sensible heattransfer to take place between the air and the thin film of water on thewetted surfaces.

To maximize evaporative heat transfer efficiency, all the surfaces ofthe direct or indirect heat exchanger should be evenly and uniformlywet. Heat exchangers that are partially or insufficiently wetted cause aloss of heat transfer and make it more likely that there will be foulingon the heat exchanger surfaces.

One design of a spray water distribution system design is a pressurizedpipe spray system with or without spray nozzles. Another design is anopen top, gravity drain water collection basin with plurality of spraynozzles or spray holes through where the top water basin delivers waterdownward by the gravity from the head of water height within the basin.This invention deals with the design of gravity drain water collectionbasin spray system without using any nozzles.

It is an object of the invention to allow for even and uniform wettingof the direct or indirect heat exchanger with evaporative fluid, usuallywater, coming from the gravity drain water collection basin spraysystem. It is another object of the invention to reduce the number ofholes in the gravity drain basin water spray system which allows forlarger diameter holes creating less chance for the holes to clog orallow for less frequent servicing of the gravity drain water collectionbasin spray system.

SUMMARY OF THE INVENTION

The present invention provides an improved gravity drain watercollection basin spray system that is used in direct or indirect heatexchange apparatus such as a cooling tower, closed circuit fluid cooler,fluid heater, condenser, evaporator, thermal storage system, air cooleror air heater.

A typical evaporative cooling tower heat exchange apparatus has a directheat exchanger, a fan system, an upper gravity drain water collectionbasin spray system, and lower sump to collect the evaporative liquid.The type of heat exchanger can be either an indirect heat exchanger, adirect heat exchanger or a combination of the two.

The indirect heat exchanger may be a coil or a plate style heatexchanger with process fluid flowing inside. The direct heat exchangercan be a fill pack which is typically made of plurality of individualthin plastic PVC fill sheets spaced apart using spacers. Fill sheets canbe either hung underneath the upper gravity drain basin water spraysystem using a hanger system or cut into smaller pieces and bundled intoplurality of small fill blocks which are then stacked on top of eachother underneath the gravity drain water collection basin spray system,each fill sheet is generally rectangular in shape and has a face and anobverse face side and also employs a surface pattern that protrudesabove and below the nominal plane of the sheet. Using spacers, fillsheets are generally separated by a nominal distance which is typicallygreater than the total height of surface pattern and generally a planeof air gap forms between two fill sheets. Spray water flows down fromthe top onto both faces of each fill sheet and adheres to the surfacecontour of each fill sheet. Because of the presence of air gap betweensheets, spray water usually does not transfer from one sheet to itsadjacent fill sheet.

A stream of air is either forced through or pulled through the fill airgaps by a fan system so that heat transfer occurs between the spraywater and air stream. Above the fill pack is gravity drain watercollection basin and typically there may be a pre-distribution box orsystem to allow for even flow into the gravity drain water collectionbasin. Water to be heated or cooled enters the upper gravity drain watercollection basin through its pre-distribution box which turns a highvelocity fast flowing water stream into a low velocity slow flowing welldistributed water stream that flows over the gravity drain watercollection basin floor. Typically there is enough water flow to back upwater a few inches into the gravity drain basin. The gravity drain watercollection basin floor has a plurality of spray holes. The combined lowvelocity and slowly flowing water coming from the pre-distribution boxallows an even and uniform amount of water travel into and through everyspray hole.

In a preferred embodiment, the spray holes are strategically locatedsuch that an equal number of holes are assigned to each face and obverseface of each fill sheet or each plate style heat exchanger. The holesassigned to each fill face are generally equally spaced apart todistribute spray water evenly on to each fill face. Because there couldbe large particles, such as rust chips and calcium carbonate chips, inthe water stream, the diameter of number of spray holes are reduced tostill allow superior water coverage onto each fill sheet while allowingfor the spray hole diameter to be enlarged to let the particles flowthrough the spray holes.

Water sprayed from the upper gravity drain water collection basingenerally flows down through each face of the fill and eventually intothe lower sump which has a water outlet where cooled or heated water canbe drained and later pumped back into the upper gravity drain watercollection basin.

It is an object of the invention to allow for even and uniform wettingof the direct or indirect heat exchanger coming from the gravity drainwater collection basin spray system. It is another object of theinvention to reduce the number of holes in the gravity drain watercollection basin spray system which allows for larger diameter holescreating less chance for the holes to clog or allow for less frequentservicing of the gravity drain basin water spray system.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a perspective view of a direct heat exchange apparatus inaccordance with the present invention;

FIG. 1A is a perspective view of an indirect heat exchange apparatus inaccordance with the present invention;

FIG. 2 is a side view of a direct heat exchange apparatus in accordancewith the present invention;

FIG. 2A is a side view of a indirect heat exchange apparatus inaccordance with the present invention;

FIG. 3 is a top view of a part of upper gravity drain water collectionbasin in accordance with the present invention;

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1 of the drawings, an embodiment of the presentinvention is shown in a cooling tower direct heat exchange apparatus 10.Direct heat exchange apparatus is comprised of casing 11, direct heatexchange fill pack 12, upper gravity drain water basin 13, lower watersump 14, water pre-distribution box 15, fan assembly 16, upper gravitydrain basin covers 17, pre-distribution box pipe inlet 18, air inlet 19and air outlet 20. It should be noted that the direct heat exchange fillpack may also be an indirect heat exchanger and is not a limitation ofthe invention. Cooling tower direct fill heat exchange apparatus 10 isgenerally enclosed in casing 11, which can be made of thin sheet ofmetal or fiber reinforced plastic. Casing 11 provides a housing for fillpack 12, upper gravity drain basin 13, fan assembly 16, and lower basin14. Upper gravity drain basin 13 is located generally directly abovefill pack 12 and fill pack 12 is located above lower sump 14. Uppergravity drain basin 13 is generally rectangular in shape having a width,length, and height. The width and length of upper gravity drain basin 13is generally the same size as width and length of fill pack 12 and theheight is usually four to 12 inches. Upper gravity drain watercollection basin 13 may be covered with a plurality of upper gravitydrain water collection basin covers 17 to prevent debris from entering.Inside upper gravity drain water collection basin 13 is pre-distributionbox 15, which sits generally in the middle of upper basin 13, butpre-distribution box 15 could be placed anywhere of upper basin 13.Water enters upper gravity drain water collection basin 13 throughpre-distribution box 15 which helps to spread water more evenlythroughout upper gravity drain water collection basin 13. Fan assembly16 draws in air through air inlet 19 and generally in crossflow throughfill pack 12 and ejects air out of direct heat exchange apparatus 10through air outlet 20. The direction of airflow may be generallyupwards, generally downwards, generally across or generally concurrentwith the water flow through the direct heat exchanger. Cooling towerdirect heat exchange apparatus 10 may have one or more water inlets 18,one or more fill packs 12, one or more fan assembly 16 and one or moreair outlets 20.

Referring now to FIG. 1A of the drawings, an embodiment of the presentinvention is shown in an indirect heat exchange apparatus 21. Indirectheat exchange apparatus 22 is comprised of casing 11, indirect heatexchange section 22, upper gravity drain water collection basin 13,lower water sump 14, water pre-distribution box 15, fan assembly 16,upper gravity drain water collection basin covers 17, pre-distributionbox pipe inlet 18, air inlet 19 and air outlet 20. It should be notedthat the indirect heat exchange section may be of any type includingtubes, plates, finned and is not a limitation of the invention. It couldalso be a combination direct/indirect heat exchange section. Indirectheat exchange apparatus 21 is generally enclosed in casing 11, which canbe made of thin sheet of metal or fiber reinforced plastic. Casing 11provides a housing for indirect heat exchange section 22, upper gravitydrain basin 13, fan assembly 16, and lower basin 14. Upper gravity drainwater collection basin 13 is located generally directly above indirectheat exchange section 22 which is located above lower sump 14. Uppergravity drain water collection basin 13 is generally rectangular inshape having a width, length, and height. The width and length of uppergravity drain water collection basin 13 is generally the same size aswidth and length of indirect heat exchange section 22 and the height isusually four to 12 inches. Upper gravity drain water collection basin 13may be covered with a plurality of upper gravity drain water collectionbasin covers 17 to prevent debris from entering. Inside upper gravitydrain water collection basin 13 is pre-distribution box 15, which sitsgenerally in the middle of upper water collection basin 13, butpre-distribution box 15 could be placed anywhere of upper watercollection basin 13. Water enters upper gravity drain water collectionbasin 13 through pre-distribution box 15 and spreads throughout uppergravity drain water collection basin 13. Fan assembly 16 draws in airthrough air inlet 19 and generally in crossflow through indirect heatexchange section 22 and ejects air out of indirect heat exchangeapparatus 21 through air outlet 20. The direction of airflow may begenerally upwards, generally downwards, generally across or generallyconcurrent with the water flow through the indirect heat-exchanger.Indirect heat exchange section 22 has internal process fluid inlet pipe23 and outlet pipe 24. The connections can be reversed if desired. Theinterior process fluid is cooled indirectly from the evaporative waterthat flows by gravity generally downward across from the upper gravitydrain water collection basin 13. Indirect heat exchange apparatus 21 mayhave one or more water inlets 18, one or more indirect heat exchangesections 22, one or more fan assembly 16 and one or more air outlets 20.

Referring now to FIG. 2 of the drawings, an embodiment of the presentinvention is shown in a side view generally as direct heat exchangeapparatus 30. Heat exchange apparatus 30 is comprised of casing 31,direct heat exchange fill pack 32, upper gravity drain water collectionbasin 33, lower sump 34, pre-distribution box 35, fan assembly 36,pre-distribution box pipe 37, air inlet 38 and plenum air outlet 39.

During operation, water to be heated or cooled enters direct heatexchange apparatus 30 through pre-distribution pipe 37, spreads acrossupper gravity feed water collection basin 33 and accumulates a head ofwater 40 inside upper gravity drain water collection basin 33. Uppergravity drain water collection basin 33 is generally an open toprectangular box comprised of sides 45 and upper gravity drain basinbottom plate 44, which has plurality of spray holes that are generallyspaced throughout. Accumulated water head 40 inside upper gravity feedwater collection basin 33 travels downward through the plurality ofspray holes in basin bottom plate 44 and forms a well distributed flow41 and falls on the top of direct heat exchange fill pack 32.

Direct heat exchange fill pack 32 is made of plurality of thin plasticfill sheet 43 that are either hung using a hanger system or bundledtogether in a block form and stacked underneath upper gravity drainwater basin 33 and above lower sump 34. Direct heat exchange fill pack32 has a plurality of air gaps so that both spray water and air caneasily flow through. When spray water flows through direct heat exchangefill pack 32 and reaches lower sump 34, water accumulates in sump 34 toform a shallow pool 42 before exiting heat exchange apparatus 30. Airenters cooling tower direct heat exchange apparatus 30 through air inlet38, travels through the plurality of gaps within fill pack 32, makesgenerally an upward turn inside plenum outlet 39 and exits cooling towerdirect heat exchange apparatus 30 through fan assembly 36. As airtravels though fill pack 32, heat exchange takes place between air andspray water on fill sheets 43.

Referring now to FIG. 2A of the drawings, another embodiment of thepresent invention is shown in a side view generally as indirect heatexchange apparatus 30A. Indirect heat exchange apparatus 30A iscomprised of casing 31, indirect heat exchange section 32A, indirectheat exchange inlet and outlet connections 46 and 47 respectively, uppergravity drain water collection basin 33, lower sump 34, pre-distributionbox 35, fan assembly 36, pre-distribution box pipe 37, air inlet 38 andplenum air outlet 39.

During operation, process fluid to be heated, cooled, evaporated orcondensed enters indirect heat exchange apparatus 30A through inletconnection 46 and exits from outlet connection 47. Evaporative fluid,usually water, enters pre-distribution pipe 37, spreads across uppergravity water collection basin 33 and accumulates a head of water 40inside upper gravity drain water collection basin 33. Upper gravitydrain water collection basin 33 is generally an open top rectangular boxcomprised of sides 45 and upper gravity drain basin bottom plate 44,which has plurality of spray holes that are generally spaced throughout.Accumulated water head 40 inside upper gravity water collection basin 33travels downward through the plurality of spray holes in basin bottomplate 44 and forms a well distributed flow 41 and falls on the top ofindirect heat exchange section 32A.

Indirect heat exchange section 32A may be made of plurality of plates43A, tubes, or finned type heat exchangers and is not a limitation ofthe invention. Indirect heat exchanger plates 43A may be either hungusing a hanger system or bundled together in a block form and stackedunderneath upper gravity drain water basin 33 and above lower sump 34.Indirect heat exchange section 32A has a plurality of air gaps so thatboth spray water 41 and air can easily flow through. When spray waterflows through indirect heat exchange section 32A and reaches lower sump34, water accumulates in sump 34 to form a shallow pool 42 beforeexiting indirect heat exchange apparatus 30A.

Air enters indirect heat exchange apparatus 30A through air inlet 38,travels through the plurality of gaps within indirect heat exchangesections 43A, makes generally an upward turn inside plenum outlet 39 andexits indirect heat exchange apparatus 30A through fan assembly 36. Asair travels through indirect heat exchanger 32A, indirect heat exchangetakes place between the spray water and the interior process fluid whiledirect heat transfer takes place between the spray evaporative spraywater and the air flowing.

Referring now to FIG. 3 of the drawings, an embodiment of the presentinvention 48 is shown in a plan view. Upper gravity drain watercollection basin bottom plate 50 has a plurality of spray water holes 51that are strategically aligned over top of a plurality of direct heatexchange fill sheets 52. Each fill sheet 52 has a front face side 55 anda rear face side 56. Each fill sheet 52 is separated by a nominaldistance determined by fill spacer 61 so that there is a gap betweenfill sheets 52. Fill sheet 52 has plurality of surface pattern humps andvalleys that may weave in and out of fill sheet nominal plane 53 andthat may not be vertically aligned when viewed downward from gravitydrain water basin bottom plate 50. The geometry and positioning of thesehumps and valleys gives fill sheet 52 a body thickness when vieweddownward from gravity drain water basin bottom plate 50. Each fill sheet52 is typically made of thin sheets of plastic or PVC but can be made ofany material desired.

Spray holes 51 are strategically aligned above the plurality of fillsheets 52 so that when spray water drops down through plurality of holes51, the water falls onto fill sheets 52. The spray water streamspurposely land on both face side 55 and obverse face side 56 of fillsheet 52. Spray holes 51 are separated by gap 70 and 72 in the width andseparated by gap 71 between the face and obverse face sides. Generallygap 72 and 70 are equal such that the number of holes are reduced. Gaps70 and 72 are at a distance apart such that when spray water hits fillsheet 52, the spray water spreads out such that fill sheet 52 isuniformly and evenly wetted. The combination of patterns, humps andvalleys in fill sheets 52 spreads the single stream of water over asurface area as a thin film of water so that more efficient air to waterheat exchange could take place. Air travels in the direction from airinlet edge 59 toward air outlet edge 60, and fill sheet 52 is aligned sothat it doesn't block the air travel.

Spacing 70 and 72 must be optimized to allow for uniform spreading onthe face 55 and obverse face sides of fill sheet 52 while simultaneouslyreducing the number of holes required such that the diameter of theholes are maximized. The hole 51 diameter and the hole spacing 70 and 72can be found by iteratively solving the following equation:Flow rate=number of fill sheets·hole spacing·hole coefficient, wherehole spacing=fill sheet air travel length÷number of holes per fill sheethole coefficient=Cd·A·(2gh)², where

Cd is drag coefficient of hole in a plate,

A is area of hole

g is gravity constant, and

h is water column height in the gravity drain water basin.

The preferred hole 51 diameter is 0.4 inches±0.2 inches while thepreferred gap 70 and 72 is 4 inches±2 inches. The balance between theselected hole diameter and selected spacing 70 and 72 vary depending onthe required overall flow rate. Once the overall target design flow rateis known, holes gaps 70 and 72 and hole 51 diameter are iterated toarrive at a solution which guarantees even and uniform water coveragewhile minimizing the number of spray holes so that the spray performancecan be maximized. This balance of finding optimum gaps 70 and 72 withhole 51 diameter guarantees maximum thermal heat transfer while reducingthe possibility for hole clogging. Hole gap 71 is selectively set toinsure both the face 55 and 245 obverse face side of fill sheet 52 areproperly covered. This gap is dependent on the gap between the fillsheets.

A set of face spray hole 57 and obverse face spray hole 58 that belongsto a same fill sheet 52 may not necessarily be in a straight line in theair travel direction. Face spray holes 57 are slightly biased towardface 55 direction from fill sheet nominal plane 53 and obverse facespray holes 58 are slightly biased toward obverse face 56 from fillsheet nominal plane 53 of corresponding fill sheet 52. The biasing ofthe holes exists so that when there is slight variation of location offill sheet 52 in a parallel direction of air inlet edge 59, both face 55and obverse face 56 are properly wetted by spray holes 51.

What is claimed is:
 1. A cooling tower comprising: an indirect heatexchange section, a water collection basin located above the indirectheat exchange section, the water collection basin having a plurality ofopenings that allow water to be distributed downwardly onto the indirectheat exchange section, the water collection basin openings beingarranged in lateral rows, the water collection basin openings eachhaving a diameter of from 0.2 inch to 0.6 inch, the spacing betweenadjacent water collection basin openings is from 2.0 to 6.0 inches, theindirect heat exchange section includes a plurality of plate type heatexchangers, each plate type heat exchanger having a centerline, a frontside, and a rear side, the front and rear sides being on opposite sidesof the centerline, each lateral row of water collection basin openingsbeing directly above a corresponding one of the plate type heatexchangers to allow water to be distributed downwardly onto thecorresponding plate type heat exchanger, wherein each lateral row ofwater collection basin openings includes a first plurality of openingsoverlapping the centerline of the corresponding plate type heatexchanger and longitudinally biased toward the front side of thecorresponding plate type heat exchanger, wherein each lateral row ofwater collection basin openings includes a second plurality of openingsoverlapping the centerline of the corresponding plate type heatexchanger and longitudinally biased toward the rear side of thecorresponding plate type heat exchanger, and wherein each lateral rowincludes an alternating arrangement of the first plurality of openingsand the second plurality of openings to evenly distribute the wateracross the front side and the rear side of the corresponding plate typeheat exchanger.
 2. The cooling tower of claim 1 wherein adjacent watercollection basin openings in each lateral row are longitudinally offsetfrom each other.
 3. The cooling tower of claim 1 further comprising atleast one fan operable to generate airflow across the plate type heatexchangers.
 4. The cooling tower of claim 1 further comprising: an inletpipe; and a pre-distribution box in the water collection basinconfigured to receive water from the inlet pipe, the pre-distributionbox permitting water to flow into the water collection basin.
 5. Thecooling tower of claim 1 further comprising a sump configured to collectwater from the front and rear sides of the plate type heat exchangers.6. A cooling tower comprising: an indirect heat exchange section, awater collection basin located above the indirect heat exchange section,the water collection basin having a plurality of openings that allowwater to be distributed downwardly onto the indirect heat exchangesection, the water collection basin openings being arranged in lateralrows, the indirect heat exchange section includes a plurality of platetype heat exchangers, each plate type heat exchanger having acenterline, a front side, and a rear side, the front and rear sidesbeing on opposite sides of the centerline, each lateral row of watercollection basin openings being directly above a corresponding one ofthe plate type heat exchangers to allow water to be distributeddownwardly onto the corresponding plate type heat exchanger, whereineach lateral row of water collection basin openings includes a firstplurality of openings overlapping the centerline of the correspondingplate type heat exchanger and longitudinally biased toward the frontside of the corresponding plate type heat exchanger, wherein eachlateral row of water collection basin openings includes a secondplurality of openings overlapping the centerline of the correspondingplate type heat exchanger and longitudinally biased toward the rear sideof the corresponding plate type heat exchanger, and wherein each lateralrow includes an alternating arrangement of the first plurality ofopenings and the second plurality of openings to evenly distribute thewater across the front side and the rear side of the corresponding platetype heat exchanger.
 7. The cooling tower of claim 6 wherein theadjacent water collection basin openings in each lateral row arelongitudinally offset from each other.
 8. The cooling tower of claim 6further comprising at least one fan operable to generate airflow acrossthe plate type heat exchangers.
 9. The cooling tower of claim 6 furthercomprising: an inlet pipe; and a pre-distribution box in the watercollection basin configured to receive water from the inlet pipe, thepre-distribution box permitting water to flow into the water collectionbasin.
 10. The cooling tower of claim 6 further comprising a sumpconfigured to collect water from the front and rear sides of the platetype heat exchangers.